Variable transformer



Feb. 12, 1952 A, SlMON 2,585,050

VARIABLE TRANsFoRMER Filed Jan, Y, 1949 -2 sHEETs--SHEET 1 uuml "MM(torneg Feb. 12, 1952 A. SIMON 2,585,050

' VARIABLE TRANSFORMER Filed Jan. 7, 1949 Y 2 SHEES--SHEET 2 GtfomegPatented Feb. l2, 1952 VARIABLE TRANSFORMER Arthur Simon, deceased, lateof Milwaukee, Wis.,

by Edna M. Simon, Clarence J. Simon, and Herbert A. Simon, executors,Milwaukee, Wis., assignors to Beatrice George Marti, Wauwatosa,

Application January 7, 1949, Serial No. 69,761

Claims. (Cl. 171-119) This invention relates to improvements in variabletransformers and particularly to transformers in which the ratio oftransformation may be changed by varying the inductance between theprimary and secondary windings while maintaining the reluctance of themagnetic circuit substantially constant.

It is one object of the present invention to provide a variabletransformer in which the output voltage may be easily varied responsiveto changes in load or to any other changes in the circuit supplied bythe transformer.

Another object of the invention is to provide a variable transformer ofwhich the output may be continuously varied rather than varied in stepsonly.

Another object is to provide a variable transformer applicable to highvoltage circuits but without contacts carrying high currents.

Another object of the invention is to provide a variable transformer inwhich the value of the secondary or induced voltage may be changedwithout phase displacement between the primary and secondary voltages.

Another object of the invention is to provide a variable transformerwith a minimum of reluctance in its magnetic circuit and in which thereluctance is maintained substantially constant at all times.

Another object of the invention is to provide a variable transformerwith relatively low magnetizing current and magnetic circuit losses.

Another object of the invention is to provide a variable transformer inwhich the windings are all substantially in planes and in which theadjacent surfaces of the cores are also substantially planes for ease inconstruction.

Another object of the invention is to provide a variable transformerwith one portion rotatable relative to another portion and in which itis no longer necessary for the rotatable portion to be kept coaxial orconcentric with the stationary portion and in which the magnetic forcesact parallel to the axis of the rotatable portion, which simplifies thcmaintaining and operation of such portion.

Another object of the invention is to provide a continuously variabletransformer which is easily adjusted, of high eiliciency, of a minimumsize for a given capacity, which is simple and inexpensive inconstruction, in which there are no circuit making and breaking contactsand whichI will be vibrationless and noiseless.

Another object of the invention is to provide a variable transformerreadily adaptable to either single phase or polyphase systems.

Objects and advantages other than those above set forth will be apparentfrom the following description when read in connection with theaccompanying drawing in which:

Fig. l is a vertical sectional view showing the invention embodied in asingle phase transformer;

Fig. 2 is a view looking at one end of the rotatable core and coilsub-assembly, rotated 90 from the position in Fig. 1

Fig. 3 is a view looking at one end of the stationary core and collsub-assembly, rotated 90 from the position in Fig. l

Fig. 4 is an exploded perspective view of the stationary core and coilsub-assembly.

Fig. 5 is an electrical line diagram showing the use of the presentvariable transformer as a feeder voltage regulator;

Fig. 6 is a view of one end of the stationary core and coil sub-assemblyof a polyphase transformer.

Fig. 7 is a view of one end of the rotatable core 1nd coil sub-assemblyof a polyphase transormer.

Fig. 8 is a series of diagrams showing the magnetic and voltagerelationships between the coils at different relative positioning of therotatable I plane surface with grooves diametrically of the core and atright angles to each other. The windings are mounted in the core groovesand divide the end of the core into pole surfaces which are defined bythe exciting windings and the compensating windings mounted below theexcited windings.

A support which is preferably non-magnetic, is formed on or mounted inthe stationary yoke and extends through the aperture in the stationarycore to act as an axle for a. rotatable portion. Such rotatablesub-assembly comprises a yoke also preferably of non-magnetic materialand on which is mounted a cylindrical spirally wound core having one endformed as substantially a plane surface and having a diametric grooveformed therein from such surface to receive secondary or excitedwindings. 'I'he yoke of the rotatable portion has a bearing for mountingsuch portion on the axle to bring the finished ends of the cores intocontact. Suitable means are provided for oscillatory movement of therotatable portion relative to the stationary portion in response tochanges in load on, or to other conditions in the circuit connected withthe secondary windings.

Referring to the drawings, reference numeral Il designates the yoke ofthe stationary portion which is preferably of non-magnetic material andis generally of spoked wheel-like form. The yoke has a flange I I and acentral boss or hub I2 with an aperture therein, the flange and bossdefining an annular space in which is mounted a core Il of magneticallypermeable, strip material wound spirally to form a hollow cylinderfitting into such space. Suitable means are provided for retaining thecore in its wound condition and for retaining the core in place on theyoke. One end of surface I1 of core Il, is preferably finished as asubstantially plane surface at right angles to the axis of the core.Grooves It and are formed in the core from the nished end thereof, andare on diameters of the core and at right angles with each other.Windings 23 and 24 are placed in the groove i9 and about the coreperiphery for severally enclosing portions ofthe core end i8 to formmagnetic pole portions 25 and 26 when the windings are energized. Otherwindings 21, 23 are placed in the groove 20 below `windings 23, 24, andabout the core periphery to compensate for stray flux as will beexplained hereinafter.

A post 3l of non-magnetic material, is ilxed in the aperture in yokeboss l2 as by use of a pin 32, to extend substantially centrally throughthe aperture in the core Il. The post serves as an axle on which ismounted a bearing 33 in a yoke 31. The yoke 31 is also preferably ofnonmagnetic material and is even more nearly of wheel-like form thanyoke Il. Yoke 31 has a peripheral flange` 3l and an aperturedcylindrical boss or hub 39 for receiving the bearing 33. A

core 43 of spirally wound magnetic strip is formed as a hollow cylinderand is retained in the annular space between the yoke flange 33 and theboss 3l, the core 43 being similar in internal and external diameter tothe core I1 and having its end surface 44 formed either as substantiallya plane or with a peripheral flange 45. A ,groove 4l is formed in thecore 43 from the end surface 44 and on a diameter of the core to receivewindings 4I and 49. Such windings form the secondary coils or excitedwindings of the transformer, in which a voltage is induced and suchwindings deiine magnetic poles 5I, li similar to the poles 25, 24.

It will thus be seen that both cores are easily and quickly made with nowaste whatever of material. It is made easier to finish one end of thecores to any desired degree of planeness than to finish core surfaces ofany other configuration. The coils are formed in planes so that thecoils also are easily and cheaply made and are readily placed in properrelation in the cores and in proper relation to one another.

Cores I3 and 43 may be in contact over their entire core ends i1 and 44thus reducing the air gap between the cores to one to two-thousandths ofan inch depending on the degree of planeness of the core ends. But therotatable sub-assembly of the transformer rests on and is to be movablerelative to the stationary sub-assembly, through a portion of arevolution about the axle 3i.

a,sss,oso Y i Hence. it may be desirable to provide one of thecoreswithabearingiiangeasatu toreduee the area of actual contact betweenthe core ends. which reduced area may then be lubricated. The amount ofrelative movement between the two sub-assemblies depends on the numberof magnetic poles employed, the movement required for the full range oftransformer adjustment. for a two-pole device being of rotation and themovement for a four-pole machine being two times 45 of rotation, etc..there being only the limit of practical usable diameter on the number ofpoles used.

Suitable means such as a gear segment Il mounted on the periphery ofyoke 31, may be engaged with gearing driven by any known type ofreversible electric motor controlled by means such as any known contactmaking and breaking meter, responsive to increase or decrease in voltage in the circuit supplied by the secondary windings 4l, 4I. The amountand rate of movement of the rotatable transformer portion beingrelatively small, it is desirable that speed reducing means be used inthe drive, which makes it possible to use a relatively small drivingmotor.

In the present structure, the yoke Il is extended to form a base, or hasconnected therewith a base I4 for a motor Il driving a worm l1 meshingwith a worm wheel Il on a shaft I3 supported in a boss 44 on the base.The worm wheel It is connected with a gear 4| meshing with the gearsegment Il on the yoke 31 of the rotatable subassembly. The gearing isalso preferably of non-magnetic material to co-act with the post 3| inavoiding a closed magnetic circuit between the yokes Il and 31, if suchyokes are not themselves formed of non-magnetic material. It is, ofcourse, understood that all of the ilux is to pass through the cores andnot through the yokes or any other portions of the device. It will beunderstood that the present operating means is i merely one of a numberof such means which may be used because all magnetic forces in thepresent device are axial of the cores, only a small movement isrequired, a relatively small weight is to be moved, the movement is atlow speed, and because of many other favorable factors in the presentdevice.

When the present device is used for feeder voltage regulation, it isconnected as shown in Fig. 5 in which a source il of alternating currentis connected to the ends of the primary windings 23, 24 which are joinedwith each other. One side of the alternating current supply circuit isconnected with a load 4I and the other side of the supply circuit isconnected through the Joined secondary windings 43, 44 with the otherside of the load 44. The compensating windings 21, 2l areshort-circuited as shown.

When the primary windings 23, 24 are energized, the core i6 ismagnetized as a horseshoe magnet" with poles 25 and 2l forming oppodtemagnetic poles. Of course, being energized by alternating current,reversal of the current reverses the polarity during each current cycle.When the primary core poles 25 and 24 are opposite the secondary corepoles 5I and Il, flux passes between the pairs of opposite polaritypoles and induces a voltage in the secondary windings 48, 49. The airgap between the poles of the several cores is constant and may be made avery small fraction of an inch dependent only on the degree of planenessof adjacent core ends. Thus the reluctance of the magnetic circuit isminimized, and is constant, which contributes to the high ei'ilciency ofthe present structure.

The electrical operation of the device can be most readily understood byreferring to the diagrams forming Fig. 8, to which are applied thereference numerals heretofore used. The cores are shown as rectangularand as reciprocably movable relative to each other and only one excitedor secondary winding and one compensating winding are shown, for ease inillustration. The flux F directly linking a primary and a secondary coiland the flux f not directly linking such coils, are shown in dottedlines and the voltage induced in secondary windings 48, 49 is shown bydot-dash arrows.

When the cores I6 and 43 are positioned as shown at A (in Fig. 8) withthe primary windings 23, 24 energized, the flux F produced by windings23, 24 is intcrlinked with secondary windings 48, 49 to induce a maximumvoltage in such windings in the direction of the arrow V in suchdiagram. Because of the fact that the cores are actually cylindrical,the flux f is not stray iiux but is also interlinked with the windings48, 49 as will be understood if the diagram is conceived withcylindrical cores and in three dimensions. Hence, the induced orsecondary voltage is a maximum in one direction and either boosts orbucks the voltage of the supply line dependent on the connections of thepresent device as is well known, it be" ing assumed that the inducedvoltage is in phase with the supply voltage in the present position ofthe parts, and therefore boosts the supply voltage.

When the parts are in position B with windings 23, 24 energized, the uxF, f induces a voltage in windings 48, 49 opposite to that produced inposition A and of the maximum value in the opposite direction. Hence,the secondary voltage V in position B is 180 out of phase with thesupply voltage and bucks such voltage. Any desired value of secondaryvoltage between the two maximums obtainable in positions A and B, can,of course, be obtained, and such voltage value is iniinitely variabledependent only on the relative position of the parts. In positions A andB, the ampere turns of the primary and secondary windings practicallyccmpensate one another.

In position C, it will be seen that the ilux about primary windings 23,24-links equally and in opposite directions with the secondary windings48,

49 thus endeavoring to induce equal and opposite voltages in suchsecondary windings. But the net eiect is zero voltage in the secondarywindings even though the flux fully interlinks the primary and secondarywindings. Hence, it will be seen that any secondary voltage from maximumin one direction to maximum in the other direction can be obtained bycontinuous variation from one maximum value through zero to the othermaximum value.

But in position C, the ampere turns of primary coils 23, 24 are notopposed by the same number of ampere turns of secondary coils 48, 49 sothat a considerable indirectly linked flux would result, which isundesirable. Such flux is avoided by the use of compensating windings21, 28 as shown in position D. The action of such compensating windingsis well known and need not be particularly described herein. However,the compensating windings have the effect in the present device ofeliminating forces acting at an angle to the axis through the coils.

When a polyphase device is desired, the primary core I6 may be made asshown in Fig. 6 for three phase use, in that it is grooved to receive anumber of pairs of windings 10 and 1|, 12 and 13, and 14 and 15 for theseveral ones of the three phases and to receive compensating windings16, 11 and 18. The secondary or rotating sub-assembly oi the deviceincludes core 43 and windings 82, 83 and 84 for the three phasesdesired. In the polyphase structure above described, the same value ofvoltage is always induced in the secondary windings but the phaseposition of the voltages is varied thus controlling the voltage supplyto the load. A polyphase unit may be connected in delta or star as iswell known, to obtain the desired phase relation. It will be understoodthat the number of poles utilized may be varied as desired merely bychanging the diameter of the cores so that the device is readilyadaptable to any required load. Increase in the number of poles producesmaximum utilization of the cores and a higher eiliciency of the device.

It will be understood that a three-phase device may also be obtained byproviding threesstructures such as are described in detail herein. Suchmultiplied single-phase device requires only that the several units bespaced sufficient distances to avoid the production of stray flux fieldsinterfering with the operation of the several units. Any desired phaserelation between the several units may be obtained by delta or starconnection thereof as desired.

It will be understood that a plurality of wind ings per pole may be usedthus increasing the capacity of the device and that such plurality ofwindings may be in side by side relation or may be fiati-cned andtwisted so as to be placed one above another. The material of the coresmay thus be utilized to any degree desired merely by increasing thenumber of windings used per phase. Even in Figs, 6 and "I, theutilization is only 50% and increase to 75% is obtainable merely by useof four primary windings per phase (spaced 120), and correspondingsecondary windings. The windings will be connected in series or parallelor series-parallel as desired.

Also it is possible to increase the capacity of a unit by using threecores with the intermediate core rotatable relative to the two end coresand with exciting or primary windings in both the end cores and coactingwith excited windings in the two ends of the intermediate core. Suchincrease in capacity does not increase the size of the driving meansrequired as is usual with other constructions.

It will be seen that the present construction provides a variabletransformer in which the cores are easily made, requiring the nishing ofonly one end of each for reducing the air gap in the magnetic circuit toa minimum and thus minimizing the reluctance of the device. The Windingsare planar and are placed in planes which simplifies the constructionthereof and the assembly of the device. All forces are axial of thedevice and press the cores together so that the yoke structure is simpleand the drive for securing rotation may be small and simple. The coresare always in contact so that the device is absolutely noiseless. Eitherone of the core-coil sub-assemblies may be made movable as desired.

The magnetizing current required and the magnetic losses are low so thata high eiiciency structure is obtained. The output voltage varies onlyin amount and there is no undesired phase displacement in the devicewhich would produce a poor power factor, and the voltage is continuouslyvariable by any desired amounts. There are no contacts carrying highcurrents and the device can be made as sensitive as desired to loadcircuit variations. ly simple and highly effective electrically atrelatively low cost and with the minimum of operating and maintenancedifficulties.

Although but a few embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

What is claimed is:

1. In a variable output voltage transformer, a pair of cores each havinga face adapted for movement in contact with a face of another core toprovide a constant and minimized airgap between the contacting corefaces, the cores being grooved from the contact faces, a plurality ofprimary and secondary windings severally mounted in the grooves of thecore, a plurality of shortcircuited windings in the grooves of one corefor compensating the stray flux of the secondary windings upon movementof the primary and secondary windings relative each other into positionsof indirect ilux linkage therebetween, and means for` moving one coreand the windings therein relative to the other core responsive tovoltage variations in the secondary windings and while the core facesare in contact.

2. In a variable output voltage transformer, a pair of cores severallyhaving a single face adapted for movement in contact with each other toprovide a constant and minimized airgap between the core faces, thecores being grooved from the contact faces, the one core being supportedwholly on the other core in superposed relation and movable thereon, aplurality of primary and secondary windings mounted in the core grooves,a plurality of short-circuited windings in the grooves of one core forcompensating the stray flux of the secondary windings upon movement ofthe primary and secondary windings relative each other, an electricmotor responsive to voltage variations in the secondary windings, andspeed reducing means connecting the motor with the upper core for movingsaid core and the windings therein relative to the lower core and whilethe core faces are in Contact.

3. In a variable output voltage transformer, a pair of cylindrical coresin base-to-base contact, one base being pressed on the other core base,the contacting bases being grooved and substantially planar for movementin contact with a base of the other core to provide a constant andminimized airgap between the contacting core bases, a plurality ofprimary and secondary wind- Hence, the device is mechanicalings eachmounted in the grooves of one of the 4. In a variable output voltagetransformer. a pair of cylindrical cores, one core being superposed onand supported wholly on the other core in basetn-base contact, thecontacting core bases being grooved and substantially planar formovement in contact with the base of the other core to provide aconstant and minimized airgap between the contacting core bases, aplurality of primary and secondary windings, the windings beingseverally mounted in the grooves of one of the cores, a plurality ofshort-circuited windings in the groove of one core for compensating thestray ux of secondary windings, means for maintaining the cores invertical axial alignment, and means for moving one core and the windingstherein relative to the other core responsive to voltage variations inthe secondary windings and while the core bases are in contact.

5. In a variable output voltage transformer, a pair of hollowcylindrical cores adapted for mounting in vertical alignment, with onebase of the pair of cores in contact, and with one core superposed onthe other core, the contacting bases being substantially planar andhaving grooves therein, the one core wholly supporting the other corefor providing a constant airgap between the adjacent core bases, aplurality of primary and secondary windings in the core grooves, aplurality of short-circuited windings in the grooves of one of the coresfor compensating the stray flux of the secondary windings upon movementof the primary and secondary windings relative each other, a pluralityof yokes severally flanged to define an annular space, the yokesseverally having central apertures therethrough, a post in the aperturesfor retaining the yokes in substantially parallel relation, an electricmotor responsive to voltage variations in the secondary windings, andspeed reducing means connecting the motor with the upper core for movingsaid core and the windings therein relative to the other core.

EDNA M. SDON. CLARENCE J. SIMON. HERBERT A. SMON.

Eecutors of the Last Will and Testament ol Arthur Simon, Deceased.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 742,548 Wright Oct. 27, 19031,445,242 Shakelton Feb. 13, 1923 1,471,863 Riegger Oct. 23, 19231,613,222 Curtis et al. Jan. 4, 1927 1,790,746 Fischer Feb. 3, 193i1,984,939 Nachumsohn Dec. 18, 1934 1,995,637 Day Mar. 26, 1935 FOREIGNPATENTS Number Country Date 246,929 Great Britain Feb. 8, 1926

